Problem: Simplify the following expression: $k = \dfrac{5r^2 - 5tr}{4r^2} + \dfrac{2tr - 6r^2}{4r^2}$ You can assume $r,s,t \neq 0$.
Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{5r^2 - 5tr + 2tr - 6r^2}{4r^2}$ $k = \dfrac{-r^2 - 3tr}{4r^2}$ The numerator and denominator have a common factor of $r$, so we can simplify $k = \dfrac{-r - 3t}{4r}$